Masons' Joints. Part 9

Grooved And Tongued Joint

This term is given to a joint between two stones connected by a long he and she joggle, or else by a groove and gunmetal tongue. There are no such alternative names as distinguish the similarly styled joiner's joint.

Grouted Joint

Grouted Joint is formed by pouring thin semi-liquid mortar or cement into a joint to fill up accidental voids and make all solid. The practice has its advocates and opponents, and no doubt if there are facilities for the superabundance of water to run off without washing away or diluting other setting mortar in its course, it may have its advantages in tending to the consolidation of the work. On the other hand, its pernicious effects must be great if the lime be drowned. Grout is requisite in deep and thin joints between large stones, but it is deficient in strength, and should never be used except where thicker mortar cannot penetrate, for too much water deprives lime of two-fifths of its strength. In some cases grouting has been advantageously poured upon the work through a long funnel, acquiring thereby the penetrative power due to a head of liquid as well as to gravitation. A key stone is more likely to have full joints by being fixed with cement grouting, and in ashlar coping to pier walls, flooring to locks or docks, and in many other parts of masonry grouting, especially if of Portland cement, is clearly a source of strength. Cement grouting between the drums of columns has already been described under Bed Joint.

Heading Joint in arch work occurs between two stones of the same string course, and therefore vertically divides the ring courses. In large arches these joints should overlap at least 12 in. In a cylindrical skew arch they con-stitute a spiral surface, twisting round the axis and intersecting at right angles the spirals of the coursing or bed joints.

Hollow Joint

Hollow Joint is necessary under window sills, as described in the Bricklayers' Section. It also often occurs over splayed window heads, as shown in Fig. 14, owing to their subsidence, which is, however, far preferable to their fracture when bedded with square ends and joints, as in Fig. 15. To obviate this unsightly and dangerous misfortune, a flat bar of wrought iron may be worked in so as to relieve the head of some of the effects of its own weight.

Fig. 14.

Fig. 15.

Horizontal Joint

This is a term for level bed, bed joint, or coursing joint when not an arch joint. In spire or other battering work the term is opposed to inclined, sloping, or raking bed joint.

Housed Joint

Housed Joint is the outcome of the operation called housing, which consists in cutting or hollowing out on the side or face of one piece of stone a sunk space exactly similar in shape to the profile of the undiminished end of the other piece which is to be let or housed into it. It does not signify whether the stones are moulded or not. Generally all parts of ornamental masonry which abut against projections are thus housed into them. The ends of stone steps are sometimes housed in a wall as much as 9 in.